1. Field of the Invention
The present invention relates to a light-emitting device including an EL sheet assembled according to insert molding.
2. Description of the Related Art
There have heretofore been proposed light-emitting devices which include an EL (ElectroLuminescence) sheet assembled according to insert molding, for emitting light from interior parts of automobiles and exterior parts of mobile phones and home electric appliances.
One such light-emitting device, disclosed in Japanese Laid-Open Patent Publication No. 2003-092189, includes a bent EL sheet having a back electrode layer and a resin-molded component integrally formed with at least the outer surface of the back electrode layer, i.e., the outer surface from which no light will be emitted. The disclosed light-emitting device is produced as follows: An EL sheet with an adhesive layer formed thereon is plastically deformed, i.e., permanently bent, to a shape including a curved portion in advance. The plastically deformed EL sheet is put into an injection mold and placed on a surface thereof which defines a mold cavity. Then, a resin is injected into the mold cavity. The adhesive of the adhesive layer is melted with the heat of the injected resin to bond the EL sheet to the resin. In this manner, the EL sheet is assembled in the light-emitting device by insert molding.
The EL sheet is very thin, e.g., has a thickness of about 0.3 mm, and hence is weak against external shocks and abrupt bending forces. When the EL sheet is plastically deformed as disclosed in Japanese Laid-Open Patent Publication No. 2003-092189, the electrode layer may possibly be damaged at a plastically deformed bent corner, tending to cause a nonluminescent portion due to a short circuit.
Furthermore, the light-emitting device disclosed in Japanese Laid-Open Patent Publication No. 2003-092189 has the EL sheet exposed on its outer surface. If the light-emitting device is installed in a switch on a motorcycle, for example, then when the light-emitting device is wetted with rainwater, light-emitting elements in the EL sheet are likely to deteriorate due to absorbed water and to lower the luminance of light emitted thereby.